Sensor Detects Differences in Plastic Materials

At the center of a new,
automated plastic sorting system is a sensor that can detect the differences
among six types of detectable plastics: PET (polyethylene terephthalate), PE
(polyethylene), PVC (polyvinyl chloride), PP (polypropylene), PS (polystyrene)
and ABS (acrylonitrile butadiene styrene).

The sorting system relies on
two sensors, a proximity sensor to detect the presence of an object in the
system, and a new plastic material sensor from IDEC. According to Lanny
Schuberg, IDEC product engineer manager, "The
plastic sensor detects different grades of plastic based upon the resonant
frequency of each plastic. Different
plastic molecules have different resonant frequencies and by tuning laser diodes
to these frequencies, they excite the molecule of the plastic and are thus
detected."

The IDEC plastic identification sensor used in the recycling system developed by IDEC, Osaka University, Mitsubishi Electric Engineering Co., Ishida Co. and Japan's Ministry of Economy, Trade and Industry. Source: IDEC.

The ability to sort plastics
properly is a major issue for plastics recycling. Current methods involve
manual, visual inspection and sorting, which is often not as accurate as needed
or infrared spectroscopic analysis, an expensive option. Behind the push to
develop this plastic sorting sensor is the desire to create a less expensive,
more accurate, automated option. Schuberg notes that accurate plastic sorting
is inherently a difficult process "because
there are many different grades and materials of plastic in the market and
different plastics recycle differently in terms of their use."

Automated Sorting
IDEC and its project partners
(including Osaka University, Mitsubishi Electric Engineering Co., Ishida Co.
and Japan's Ministry of Economy, Trade and Industry) worked together to design
and create the sorting system; IDEC claims the system is the world's first
plastic sorting system equipped with an industrial robot to be introduced at
retail stores. The system has been introduced in Japan at the Nara Co-op and
the Osaka University Co-op for people to turn in used plastics for recycling
without having to first pre-sort the items. (See System Overview graphic.)

Using a six-axis articulated
robot arm manufactured by Mitsubishi Electric Corp. and interfaced to an IDEC
controller, the sorting system is able to transfer plastic items into specific
boxes for recycling after sorting. The basic function of the system is to first
analyze a plastic item against a reference by means of the sensor's photodiode
receiving a signal captured from a mirror that directs the "image" created by laser
diodes. These laser diodes provide the light source for the sensor. Data from
the sensor is then sent to a control/signal processor in the system's
controller before being output to direct the robot arm for sorting.

A major push behind the
development of this sorting system is Japan's current policy initiative to
promote the use of the "service robots" for lifestyle support. Osaka University
is also a principal supporter of the move toward more plastic recycling as part
of its goal of contributing to the creation of a low-carbon society.

Carbon Reduction
"This
project started with a grant from the Japanese government to IDEC, which then
started working with Osaka University researchers in this area," says Schuberg.
Other partners, like Mitsubishi, were brought in to add their particular
expertise.

Carbon reduction is a major
component of this project because plastic production is one of the leading uses
of petroleum. "By reducing the amount of plastics produced, we would use less
oil, and therefore reduce the amount of CO2 created to produce
them," says Schuberg. Though this is a major issue of concern in Japan,
Schuberg points out that California bill AB32 specifically calls for a reduction
in greenhouse gasses, and a number of other Congressional bills are pending in
this area, which could make plastics recycling in the U.S. as significant an
issue here as it is now in Japan.

Source: IDEC

Schuberg says that IDEC is gauging the market potential for the sensor in the U.S. "At the moment,
we have a very promising opportunity with the state of California to detect bio-plastics,
but this is in the initial stage," he says. Potentially, the system could be
used in recycling plants, as well as being set up in retail or collection
centers.

Though the current vision for
this sensor is plastic detection and recycling, "the sky is the limit for this
detection technology," Schuberg says, "as the lasers can be tuned to detect
resonant frequency of many different objects."

Laser and Photonics Expert Plays
Leading Role
Satoshi Kawata, a
professor in the Department of Applied Physics at Osaka
University and the center director professor in The
Photonics Advanced Research Center (PARC) at Osaka University, worked with IDEC and other partners on the development
of the laser sensor application for plastic identification and sorting. Kawata is known for his work in nanophotonics
(study of the interaction between photons and nanostructures).
In his career, he has contributed to a number of inventions, publications, and
conference organizations in fields including near-infrared spectroscopy,
laser-scanning microscopy, near-field
optics, plasmonics, biophotonics, laser nanofabrication and signal
recovery.

PARC
was established by the president of Osaka University in July 2007 and is
sponsored by the Ministry of Education, Culture, Sports, Science and
Technology, Japan (MEXT). For more information on PARC, visit: http://parc.eng.osaka-u.ac.jp/english/

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